How Often Should I Change My Oil?

The articles one finds online try very hard to be definitive – which is why they’re often inaccurate. For example, I recently came across an article that stated with the certainty of the Dear Leader that “savvy car owners know that changing the oil on their vehicle every 3,000 miles is overkill and a waste of money.”

And also that “…most vehicles built in the last twenty years can go 7,500 to 10,000 miles before a change of oil and oil filter is needed.”

Well, actually, not necessarily.

The honest answer about oil and filter changes is – it depends.

It depends, for one, on your particular vehicle. And it also depends on how that vehicle is driven – including when it is driven, how often (or not) and under what conditions. It depends on the type of oil and filter you use, too.

Just for openers.

1) Consider your vehicle.

The universal statement that you are “wasting money” if you change your oil every 3,000 miles could lead to wasting a lot more money – on engine work – if it goes against what’s right for your particular car.

If you have a car built before the late 1980s, for example it may still be necessary to change the oil every 3,000 miles – just as the factory recommended when it was new. The chief reason being that cars of this vintage (and older) have carburetors rather than fuel injection, which is a less precise way of metering fuel to the engine. Rather than a high-pressure mist, fed to the engine in just the right ratio, a carburetor may be running “rich” (feeding he engine too much gas) and some of the gas may still be in liquid form. Too much gas – and any “raw” gas – will often make its way to the oil sump in the bottom of the engine, where it will act as a solvent, washing the protective film of oil off critical parts and diluting the oil’s ability to protect the engine.

You don’t want gas in your oil – and only draining it will get rid of it.

Or, your vehicle may be newer and equipped with EFI – but also have a lot of miles on it. In which case, the engine may not be as tight as it was when new. In which case, contaminants (such as blow-by, which gets past worn piston rings) accumulate in the oil faster than they used to . In which case, you ought to shorten oil/filter changes to extend the useful life of the engine as well as get optimum mileage out of it.

2) Take into account how do you drive it.

A car that is infrequently driven should have its oil changed more often even if the miles haven’t accumulated to the recommended changeout interval – for similar reasons to those discussed above. Corrosive acids and condensation can form inside a lightly-used engine and if it’s not boiled off by use (or captured by the filter as the oil circulates through the system) it will accumulate to the point that the oil needs to be drained to get the contaminants drained. Lightly-used engines are also more prone to sludge build-up. If you have a vehicle you just use to run to the store that’s a mile down the road and back – and that’s it – you probably ought to shorten your oil/filter changeout intervals.

And of course, the opposite sort of use – that is, hard use – is another reason to reduce service intervals. Most automakers specifically recommend this in the owner’s manuals they give you with the car. The problem is that some people don’t read the manual and so have no idea that their slow-motion, bumper-to-bumper commute to work and back each day constitutes “severe” or “heavy duty” use – and that the advertised 5,000 or even 10,000 mile changeout intervals are only for “normal” driving conditions.

Read your manual. Be sure.

3) Account for the type of oil and filter.

This one’s probably the most important factor of all. If you use the lowest-price, bulk-bought, no-name-brand, who-knows-where-it-came-from oil and filters you could be risking engine damage just by starting it – let alone using that stuff for 5,000 or (forget about it) 10,000 miles. Especially if your car was designed to use semi (or fully) synthetic oil and high-performance filters. In fact, using less-than-the-minimum recommended quality of oil, or a filter that does not meet the vehicle manufacturer’s specifications for flow or size of particles captured, pressure capacity, durability, etc. can void your warranty coverage and leave you holding the bag (of parts) if your engine grinds itself to death as a result of an oil or filter-related failure.

There is also the issue of viscosity – thickness, or flow resistance. Modern engines have very tight internal tolerances, which is one of the reasons (in addition to reducing friction) why the vehicle’s manufacturer may recommend a very specific viscosity, such as 5W-30 rather than a heavier 10w-40. If you make the mistake of using the heavier oil because “it’s what they had” or “it was on sale,” you may end up learning the hard way – the expensive way – how important it is to use the recommended viscosity oil, as well as the recommended quality oil.

Conversely, if you use very high-quality oil – especially semi and full synthetics and top-drawer filters such as those made by Ames, Mobil 1 and so on – then you probably can go for longer (and run your car harder, too) without much, if any, risk to your engine.

Synthetics will usually give you noticeably better cold-start performance and driveability, too. But they’re expensive – typically 40-50 percent more per quart than conventional mineral oil. Ditto the filters.

So, the Catch-22 here is that while you can go longer between oil/filter changes, each oil and filter change will probably cost you significantly more. In the end, your net cost may be about the same – though you’ll save some time by not having to change the oil/filter quite as often.

Whichever type/brand of oil (and filter) you use, be absolutely sure it meets the vehicle manufacturer’s minimum SAE requirements before you use it. The SAE rating will be listed in your vehicle owner’s manual.

The opinions expressed in posts to the NMA Blog belong to the author and do not necessarily represent those of the National Motorists Association or the NMA Foundation. THe content of the NMA Blog is for informational purposes only and is not intended as legal advice. No representations are made regarding the accuracy of NMA Blog posts or of links found within those posts.

2 Responses to “How Often Should I Change My Oil?”

The only "true" way is to perform UOA (Used Oil Analysis)… of course, such efforts are rather overkill for most people since it costs time and money to do that. I perform these on my car because I drive it rather hard and it's turbocharged. However, since I use synthetic, I seem to be fine to carry it on for over 7500 miles without issue (mfg suggests 3750).

That being said, most modern cars can go 6000 miles without any issues, even on regular oil. If you really want to dig into it, BITOG is a great resource, and the forums there can get yourself REALLY anal about the process: http://www.bobistheoilguy.com/

In my experience, even on my older car (non turbo)… I was going 6000 miles without issue, and with good UOA results. I recommend at least 6000 miles on most cars these days, because I haven't seen a single one which required less.

and that's just trying to find people using standard oils (non-synth, even though #2 is a blend). The point is, standard oils are pretty darn good these days… on a modern car, it's not even worth looking at until 6k miles, in my opinion.

Of course, don't go taking my advice blindly. Ideally, you should check YOUR car. And you should be aware of any warranty issues with doing this. I voided my warranty with modifications about 2 months after I bought it, so I knew I didn't need to keep to the crazy-short oil change schedule.

In the end, don't come crying to me if your car breaks down. >> I << have had no issues with 6k oil changes…

My car use was aprox 80 miles/day(5days) to work & back, steady driving around 60mph with
no stop&go. I used 5w-30 Amsoil with their filter and ran about 22K yearly. They advertise oil good for 25K or 1year which I tried with excellent results.
I also used an oil analysis service and sent them a sample when oil was changed for 1st 3 years.
I changed oil/filter YEARLY without any problems and the analysis was shown above standards for all items tested. The car was a '71 Datsun 1200 and is still running but on its 2nd engine. Original ran 260K before worn out and was then replaced.
Just the facts Ma'am! (Dragnet)